An insulated-gate bipolar transistor, hereinafter referred to as IGBT, is a three-terminal semiconductor device primarily used as an electronic switch and may combine high efficiency and fast switching. The IGBT may switch electric power in many applications, e.g., appliances such as electric cars, trains, variable speed refrigerators, air-conditioners and many more.
The IGBT combines the gate-drive characteristics of a MOSFET with the high-current and low-saturation-voltage capability of bipolar transistors by combining, in a single device, an isolated gate field effect transistor (FET) for the control input and a bipolar power transistor for switching.
The IGBT can exhibit power loss in the on-state and during switching. For instance, minority carriers (holes) may take time to recombine or to leave the device, resulting in longer switching times and higher switching loss. Increasing the external gate resistance to avoid steep flanks of the switching characteristic can further delay this process. The static losses in the on-state may be reduced by increasing the electron-hole concentration (plasma concentration) in the device. This, however, leads to a further increase of the dynamic losses due to the above-described effect, and there is a trade-off between static and dynamic losses.
Therefore, there is a need for improved semiconductor devices and improved methods relating to the operation and manufacture of semiconductor devices, wherein the switching losses are reduced without significantly increasing the static losses.